This invention relates generally to program controlled manipulators and particularly to controlling the motion of a tool or other article carried by a manipulator.
It is recognized that for ease of programming, the positions and motions of a manipulator are most suitably described with reference to a rectangular coordinate system. This is particularly true where the manipulator structure includes axes of motion which do not correspond to the conventional three-dimensional coordinate system. Examples of such machines include the so-called anthropomorphic and articulated machines.
Because articulated machines would, except for coordination of machine axes motion, produce paths not intuitively expected in moving the tool from one position to another, it is also recognized that the tool motion is preferably produced by controlled interpolation of intermediate points along a path predefined in space with respect to the rectangular coordinate system. This type of control requires that the coordinates of the interpolated intermediate point be transformed to coordinates of the machine axes in order to produce coordinate motion of the machine axes to follow the predetermined path. A method and apparatus for accomplishing this type of controlled path motion is disclosed in U.S. Pat. No. 3,909,600.
The interpolation process therein described is subject to two drawbacks. First, in order to produce controlled acceleration and deceleration to accommodate the machine inertia, all variable velocity subspans are precomputed according to a selected number of predictable cases and limited to constant acceleration functions. Further, the preexecution computation requries looking ahead to subsequent position data to achieve the best velocity performance over serial spans. The entire precomputation process is cumbersome and time consuming; and because of the constant or single valued acceleration function, discontinuities occur when changing to and from the acceleration and deceleration subspans. Secondly, because the velocity characteristics of each span are precomputed, this system is not susceptible of an instantaneous velocity override as may well be appropriate in some manipulator applications.
It is therefore, an object of the present invention to provide an articulated manipulator and control for controlling motion of a function element along a predetermined path at a velocity instantaneously variable throughout the motion.
It is a further object of the present invention to provide an articulated manipulator and control for controlling motion of a function element along a predetermined path and subject to a continuously variable velocity.
It is a still further object of the present invention to provide an articulated manipulator and control for controlling motion of a function element along a predetermined path at a variable velocity subject to variable acceleration and deceleration values.
It is a still further object of the present invention to provide an articulated manipulator and control for controlling motion of a function element along a predetermined path at a continuously variable velocity subject to a continuous function of acceleration and deceleration responsive to the preprogrammed description of motion.
It is a still further object of the present invention to provide an articulated manipulator and control for controlling motion of a function element along a predetermined path at a velocity subject to variations according to a parameter independent of the preprogrammed description of motion.
Further objects and advantages of the present invention shall become apparent from the accompanying drawings and description.